[histv7] provide only I/O constructor
[histv7] provide only I/O constructor

Now it can be used to read interprted class from ROOT file

olifre/root,root-mirror/root,karies/root,root-mirror/root,karies/root,karies/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,root-mirror/root,olifre/root,karies/root,karies/root,root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,root-mirror/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,olifre/root